Right Heart Cath

Review data that can be obtained from a right heart cath and interpretation of those numbers:

With a right heart cath (or swan), you can directly measure pressures in the RA, RV, PA, and wedge.
Normal values (rule of 5’s):

• RA: 5 mmHg
• RV: 20/5 mmHg
• PA: 20/10/15 mmHg
• PCWP: 10 mmHg
• Cardiac output: 5 L/min, index: 3 L/min

Cardiac Output - measurement via Fick Method = O2 consumption / 10 (Arterio-venous O2 difference = 1.34 x Hb x Arterial O2 sat - mixed venous O2 sat)
Keep in mind for the Fick that O2 consumption is typically estimated based on the patient's weight, as well as age, sex, height, so the main weakness of this method is in patients who have an abnormal level of O2 consumption (like critically ill patients with sepsis).

The other main method for CO measurement is the Thermodilution method, whereby a known volume of saline at a known temperature is injected into a proximal port in the RA, and the temperature is measured at the distal port in the pulmonary artery.  CO is inversely proportional to the change in temperature (i.e. a large change in temperature corresponds to a low cardiac output).  Main problems with this are inherent variability, also unreliable with tricuspid regurgitation and R-L or L-R shunts.

With the above numbers, you can calculate (not directly measure) the SVR (systemic vascular resistance) which equals 80 x (MAP - CVP)/CO.  Remember that the SVR and PVR are calculated values, not directly measured.

Last note is that our CCU uses the Fick Method, while the Stanford ICU usually uses the thermodilution method.

(Christopher Woo MD, 1/21/11)

(Chanu Rhee MD, 6/11/10)